Video-on-demand (VOD) is a system of providing video program material immediately upon request to a subscriber. Frequently, VOD is used in hotel rooms to provide guests with pay per view movies. In a typical VOD system, a bank of video tape recorders has program material queued and ready for transmission to a requestor, who may be several miles away.
In U.S. Pat. No. 5,410,343, Coddington et al. disclose a VOD system which relies upon telephone lines for distribution. In particular, use of asymmetric digital subscriber line (ADSL) telephone channels is disclosed, together with use of the public switched telephone network for delivery of video program material. ADSL channels are bi-directional digital telephone links having a 1.54 Mbps bandwidth in one direction and a 9600 bps bandwidth in the opposite direction. ADSL can be transmitted on ordinary wire pairs and cable is not required.
The system described by Coddington et al. represents a significant leap in the distribution of video program material because the public switched telephone network is ubiquitous, whereas cable networks are not. While cable networks may include telephone channels, the opposite has not been true, and previously it was thought that only cable networks had sufficient bandwidth at the subscriber level for video program material, especially for VOD.
Two problems are encountered with video-on-demand. The first is that there is a large capital expense associated with generating each program channel, known as a video thread. This is because each channel is dedicated to a particular user from the video server to the destination settop box. The second is that a large demand for the same video program is difficult to service, because capital equipment for generating each program channel is limited.
What is needed is a distributed approach to video-on-demand which uses the public switched telephone network, yet is not reliant on dedicated resources for each subscriber channel and this is the object of the present invention.